1. Field of the Invention
The present invention relates to a conductive thermoplastic resin, and especially relates to a conductive polyphenylene ether-polyamide blend.
2. Brief Description of the Related Art
Poly(phenylene ether) resins (referred to hereafter as xe2x80x9cPPExe2x80x9d) are commercially attractive materials because of their unique combination of physical, chemical, and electrical properties. Furthermore, the combination of these resins with polyamide (PA) resins into compatibilized blends results in additional overall properties such as chemical resistance, high strength, and high flow. Examples of such compatibilized blends can be found in U.S. Pat. No. 4,315,086 (Ueno, et al); U.S. Pat. No. 4,659,760 (van der Meer); and U.S. Pat. No. 4,732,938 (Grant, et al). The properties of these blends can be further enhanced by the addition of various additives such as impact modifiers, flame retardants, light stabilizers, processing stabilizers, heat stabilizers, antioxidants and fillers.
The physical properties of PPE/polyamide blends make them attractive for a variety of end-use articles, for example, in the automotive market, for various exterior components. Dimensional behavior of these components is critical due to the differences in coefficient of thermal expansion, which can be improved by adding fillers (organic/inorganic) as known to those skilled in the art.
U.S. Pat. No. 5,591,382 to Nahass et al., discloses a polymeric composition comprising carbon fibrils, at least a portion of which are in the form of aggregates, wherein, as measured on an area basis, substantially all of the aggregates are less than about 35xcexc in diameter. The polymeric composition is prepared by combining the carbon fibrils with a polymeric material, mixing the combination to distribute the fibrils in the polymeric material and applying shear to the combination to break down the aggregates until substantially all of the aggregates are less than about 35xcexc in diameter. Nahass et al. teach the use of a lower loading of the conductive fibrils in order to achieve a certain conductivity while retaining better impact performance compared to carbon black or carbon fibers.
Although numerous PPE/polyamide compositions having a variety of properties are available, compositions having alternative properties are continuously sought in the industry.
The present invention relates to a thermoplastic resin composition and a method for making the same. The composition comprises: about 10 weight percent (wt. %) to about 50 wt. % polyphenylene ether, about 35 wt. % to about 65 wt. % polyamide, about 5 wt. % to about 40 wt. % talc, and about 0.4 wt. % to about 3.0 wt. % carbon.
The method comprises: forming a talc masterbatch comprising about 40 wt. % to about 50 wt. % talc and about 50 wt. % to about 60 wt. % polyamide; forming a carbon masterbatch comprising about 10 wt. % to about 30 wt. % carbon and about 70 wt. % to about 90 wt. % polyamide; introducing polyphenylene ether and a compatibilizer to an extruder; maintaining the extruder at a sufficient temperature to melt the polyphenylene ether; introducing polyamide, said carbon masterbatch to the extruder at a downstream port; forming a thermoplastic composition comprising the reaction product of about 10 weight percent (wt. %) to about 50 wt. % polyphenylene ether; about 35 wt. % to about 65 wt. % polyamide; and about 0.4 wt. % to about 3.0 wt. % carbon.